Ive tried several times to find just whom makes scale chain and couldnt come up with anything either. Not even the jewelery type chain gets small enough to match prototype chain in HO, close but not qute close enough. Ive also walked through craft stores trying to find the small stuff in thier department of necklace chain type products.
When you hold this 40L stuff up to the light, it makes you marvel how the hell they can even make this and for a couple of bucks a foot as well! When I was looking for the 32, I came across one place that made miniature double row drive chain for scale machinery and single row for scale motorcycles.
Might have to go and scoure some of the local pawnbrokers and Op shops.